Investigating the Southwest Rift Zone of Mauna Loa Volcano using gravity: what created the Ninole Hills?

Volcanic rift zone reorganization and massive underground magma chambers are required to solve the mystery of Mauna Loa’s Ninole Hills. Mauna Loa’s lava flows repave 90% of the surface every 4,000 yrs, finding 100,000 yr old rocks is a geological detective sleuthing game.

Dr. Jeffrey Zurek (P.Geo) marks the 10 yrs of his research in Geophysical Research Letters by diving into the geophysics of Hawaii. Using high-precision Bouguer gravity mapping, he reveals how catastrophic mass wasting events can knock a volcanic rift zone off its axis, preserving ancient topography and reshaping the evolution of basaltic island volcanism.

Topics

The Survival of the Ninole Hills: Why these ancient outcrops shouldn't exist on the surface of this active shield volcano

Gravity Anomalies Explained: How "boxes with springs" allow geophysicists to detect high-density olivine crystal accumulations

Failed vs. Migrated Rifts: Mauna Loa’s southwest rift zone likely once had a completely different orientation

Landslide Trigger: Mass wasting 600 cubic kilometers can geologically "instantly" shift a volcano’s internal stress regime

Chapters

(00:00) 10-Year Anniversary My Research

(02:40) Hotspots: Stationary Plumes vs. Moving Plates

(03:45) Basics of Isostasy: The Pool Floaty Model

(05:10) Convection, Ridge Push, and Slab Pull

(06:50) Shear Waves: How We Know the Mantle is Solid

(08:30) 90% of Mauna Loa's Surface is less 4000 yr old

(12:30) The Subsurface Density of the Ninole Hills

(14:45) Anatomy of a Rift Zone: Intrusions and Instability

(16:20) Dismissing the Proto-Volcano Hypothesis

(18:30) Fieldwork in Hawaii: Gravimeters and GPS

(20:15) Settling Olivine: Signature of Magma Chambers

(22:00) Triple Junction Physics: Rifts Prefer 120 Degrees

(23:45) Kilauea’s East Rift: Asymmetric Gravity Signals

(25:30) Geologically Instantaneous Migration Events

(28:00) West Flank Landslides: 240,000 yrs ago

(30:15) Comparing Mauna Loa to Tenerife’s Angara Volcano

(31:45) Impact on Global Island Volcanism

(32:30) Volcanic Faults: The Dad Joke Segment

Links

HVO: https://www.usgs.gov/observatories/hvo

Research Paper doi: 10.1002/2015GL065863

Email: whimsical.wavelengths@gmail.com

Support: Pateron

Socials: Bluesky | Instagram | Facebook

Whimsical Wavelengths: Deep-dive conversations where a working scientist unpacks how we know what we know, one paper, one idea, or whimsical detour at a time. Hosted by Dr. Jeffrey Zurek (P.Geo).